It’s hard to tell who is more frustrated at this point: Microsoft, which has been trying to simplify the upgrade process to Windows 10 as much as possible; or users, who don’t believe it could be that easy.

On Friday, Microsoft’s Gabe Aul tried to explain that users would need a Microsoft account to upgrade to the latest Windows 10 preview builds, as well as the RTM version, which will be released on July 29. Implicit in that post was the assumption that users would upgrade from a genuine Windows 7 or Windows 8 PC to Windows 10 via the Windows Insider program.

Some users apparently believe they might be able to upgrade a Windows XP or Windows Vista PC to Windows 10, however, simply by upgrading to Windows 10 from a Windows 10 ISO file before the Insider program expires. That is not true, Aul said. “Friday’s post was intended to clarify how the Windows Insider Program will proceed, and in attempting to do so created some unintended confusion,” Aul wrote on Monday, in what was essentially a do-over.

Why this matters: It’s hard who to know who’s really to blame. I’m told that Microsoft is trying to let users know that Windows 10 will be free—to consumers, not enterprises—without involving its legal team. Users, meanwhile—and that includes cynical reporters like me—wonder whether Microsoft is waiting to spring some “gotcha” on us at the last minute. I’m still hoping that Aul authors a post titled ‘Windows 10 is free, free, free,” so we can put all this to rest.

Windows Insiders have two choices

For the Windows Insiders helping to test Windows 10, there are two paths: Those who wish to keep receiving and trying out Windows 10 preview builds, even after the RTM version is shipped out on July 29; and those who wish to opt out after July 29.

For those Insiders who wish to opt out on July 29: For this group, the experience will be essentially the same as for those who’ve purchased a brand-new Windows 10 PC, assuming you own a genuine Windows 7 or Windows 8.1 license. (If you pirated Windows 7, you don’t.) Your license will be valid for the “lifespan” of that device—whatever that ends up meaning.

But that also means Windows Vista owners are out of luck. Even though you helped Microsoft test Windows 10, you’ll need to buy a retail copy of Windows 10.

There’s another caveat: You have to take the plunge and install Windows 10 as your primary operating system. Assuming Microsoft’s Gabe Aul is correct, if you run Windows 10 within a virtual machine, you won’t be eligible for the free upgrade.

@sergiocastell96 you would need to install 10130 as your main OS, or if your main OS is Win7 or 8.1 then just upgrade normally.

For those who wish to continue as Windows Insiders: ”Since we’re continuing the Windows Insider Program you’ll be able to continue receiving builds and those builds will continue to be activated under the terms of the Windows Insider Program,” Aul wrote.

Basically, because Insiders are continuing to help test Windows 10, they’ll continue to receive new builds. Those builds will expire after a while, but a fresh build will always be there to take its place, Aul wrote. Insider are receiving Windows 10 for free. The tradeoff, of course, is that new Windows 10 builds usually break something, so there’s always a chance of some inconvenience.

Here’s the puzzler: Windows 7, Windows 8.1, and Windows Vista owners are eligible to test Windows 10 as an Insider. So Windows Vista owners should get the benefits of Windows 10 without needing an upgrade. Microsoft hasn’t said anything about cutting off Vista owners at a later date from Insider upgrades.

It’s time for some new hardware, Vista owners

If you’re running Windows Vista and opt out of the Insider program, it appears you’ll have to pony up for a new license. Sorry.

“This is not a path to attain a license for Windows XP or Windows Vista systems,“ Aul wrote. “If your system upgraded from a Genuine Windows 7 or Windows 8.1 license it will remain activated, but if not, you will be required to roll back to your previous OS version or acquire a new Windows 10 license. If you do not roll back or acquire a new license, the build will eventually expire.”

Seriously, however, if you do own Windows Vista, it’s time to upgrade. A mid-range PC costs a just a few hundred dollars—probably less than what you paid for a decent Windows Vista system. Running a modern OS, Windows 10, on ancient hardware will simply become more and more painful. If you're still on Windows XP or Windows Vista, though, please tell us what you think in the comments.

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